Conventionally, as a mode of a super-micro bubble generator, there has been known a super-micro bubble generator disclosed in patent literature 1. That is, patent literature 1 discloses a micro-bubble generating device where in the inside of a cylindrical casing body which has an introduction opening through which a liquid is introduced therein on one end thereof and a delivery opening through which the liquid is delivered therefrom on the other end thereof, a gas-liquid mixing part; an enlarged diameter flow path forming part; a swirl flow forming part; and a temporarily retaining part are arranged sequentially toward the delivery opening from the introduction opening. In the gas-liquid mixing part, a gas is introduced into the inside of the casing body through a suction opening formed in a peripheral wall of the casing body and is mixed with the liquid. In the enlarged diameter flow path forming part, the diameter of the enlarged diameter flow path forming part is gradually enlarged toward a delivery opening side from the gas-liquid mixing part. The swirl flow forming part is connected to a terminal end portion of the enlarged diameter flow path forming part, and forms a gas-liquid mixed phase into a swirl flow. The temporarily retaining part temporarily retains a swirl flow formed by the swirl flow forming part.
Micro bubbles are generated by the micro bubble generating device as follows. That is, a liquid introduced into the casing body through the introduction opening and a gas introduced into the casing body through the suction opening are mixed together in the gas-liquid mixing part thus forming a gas-liquid mixed phase. The gas-liquid mixed phase is made to pass through the enlarged diameter flow path forming part so that the gas-liquid mixed phase is decelerated whereby a gas-liquid mixture flow is formed. The gas-liquid mixture flow is guided to the swirl flow forming part and is formed into a swirl flow. At this stage, the gas which forms the gas-liquid mixture flow is dispersed in the form of fine gas bubbles. Then, the swirl flow is temporarily retained while flowing in the temporarily retaining part so that relatively large bubbles are crushed. Thereafter, the swirl flow containing fine bubbles (micro bubbles) is delivered from the delivery opening.